This application claims priority benefits based under 35 USC xc2xa7119 of Japanese Patent Application Serial No. 11-275829, Japanese Patent Application Serial No. 11-275830 and Japanese Patent Application Serial No. 11-275831, the disclosure of which is incorporated by reference.
1. Field of the Invention
The present invention relates to a rolling bearing filled with a polymer containing a lubricant.
2. Description of Related Arts
In a paper making machine, for example, a paper web is pulled with a pair of ropes attached to either corner of the leading edge thereof, thereby to pass through paper making processes sequentially. The paper passes through rollers while the ropes are wound successively around a number of carrier wheels. The carrier wheels are supported freely rotatably by rolling bearings.
The rolling bearings for the carrier wheels are subjected to a severe operating environment particularly in a dryer section where the paper is dried. In the dryer section, temperature and humidity may be as high as 100 to 120xc2x0 C. and 100%, respectively, while the rolling bearings may be directly exposed to water splash.
Although the rolling bearings described above are provided with ordinary sealing members, rolling bearings are intrinsically difficult to seal completely even with the sealing member, due to the construction thereof. Thus water may enter the rolling bearing thereby causing rust therein.
To counter the problem described above, the inside of the rolling bearing may be filled with grease. This will have a rust prevention effect since the grease that fills the inside prevents moisture from entering the inside of the bearing. But the grease increases the torque required to rotate the bearing. Also because it is difficult to completely seal the bearing as described above, part of the filling grease may leak to the outside due to thermal expansion or other cause.
Meanwhile, there are rolling bearings of such a type as where a resin is impregnated with a lubricating oil so that the bearing is lubricated by the lubricating oil that oozes out of the resin. However, when the rolling bearings of this type are used for the application described above, moisture that enters the bearing leads to rusting and causes the service life to be even shorter than that of the grease-filled rolling bearing.
Similar problems are encountered in the cases of bearings used in a conveyor of a continuous car washing machine that carries vehicles on the conveyor and washes the vehicles continuously, bearings for the rolls of the pickling line of a steel mill, wheel supporting bearings of an agricultural vehicle and wheel supporting bearings of an unmanned vehicle automatically operated in and outside of a factory.
An object of the present invention is to provide a rolling bearing which is not likely to rust even in a severe environment or allow lubricant to leak, and rotates with a low torque.
In order to achieve the object described above, a preferable aspect of the present invention is directed to a rolling bearing comprising: first and second races that define an annular space (7) formed therebetween; a plurality of rolling elements arranged in the space and rolling on each of the races; and rust-preventive means that prevent rust from being generated in the space; the rust-preventive means containing a solid lubricant composition, with which the space is filled; the lubricant composition containing a resin polymer.
In this case, since the bearing is lubricated by a lubricating agent that oozes out of the lubricant composition, greasing is made unnecessary while achieving a low torque. At the same time, the lubricating agent prevents the rolling elements and the races from rusting.
The space at least in a region of which that encloses the rolling elements is preferably filled with the lubricant composition, while the rust-preventive means further includes a pair of sealing members which are arranged between corresponding end portions of the pair of races and seal the space, and grease with which a region between the lubricant composition and the corresponding sealing members in the space is filled.
In this case, since the lubricant composition that covers the rolling elements is further covered by the grease, moisture can be prevented from entering the space and, as a result, it is made possible to prevent rust from being generated and elongate the service life of the bearing. Also, because the amount of the grease filling the region not occupied by the lubricant composition in the space is small, there is no possibility of the lubricating oil leaking to the outside as in the bearing filled with grease throughout the space.
Also, a vapor phase rust-preventive agent is preferably added to the lubricant composition. This makes it possible to prevent rusting by the action of the vapor phase rust-preventive agent even when moisture enters the space, thereby elongating the service life of the bearing. The vapor phase rust-preventive agent exerts a rust preventive effect continuously in a large region in the space that includes the vapor phase rust-preventive agent and has particularly great effect of preventing rust from being generated.
Also a first additive containing a metal sulfonate and a second additive containing sorbitan are preferably added to the lubricant composition. In this case, even when moisture enters the space, rusting can be prevented from occurring by the action of both additives thereby elongating the service life of the bearing. Combined use of the first additive containing a metal sulfonate and the second additive containing sorbitan achieves particularly great rust prevention effects.